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在复杂地层钻进时,地层中的气体会以重力置换、欠平衡气侵等方式进入井筒,现有的气侵检测方法主要有泥浆池液面监测、地面出口流量检测和气侵声波时差监测,但这些方法存在气侵检测效率低、不能进行早期识别预警等多种问题。针对气侵早期识别困难的难题,在考虑侵入气体物性随井筒中温度、压力变化的基础上,结合地层渗流,建立了气侵井筒传热与多相流动瞬态模型,给出了数值求解方法。通过对该模型求解,计算结果表明:在气侵过程中井底压力不断降低,并且随着气侵时间的增加,井底压力减小速率加快,与此同时,井底温度不断升高,环空返出口温度不断降低。根据该变化规律提出了以井底压力与井口温度相结合或井底温度与井底压力相结合进行气侵早期检测的新方法。
When drilling in complicated formations, the gas in the formation will enter the wellbore by means of gravity replacement and underbalanced gas invasion, etc. The existing methods for detecting gas invasion include mud pool level monitoring, ground exit flow rate detection and gas intrusion sound wave time difference monitoring, However, these methods have the problems of low efficiency of gas intrusion detection and failure of early identification and early warning. Aiming at the difficulty of early identification of gas invasion, a transient model of heat transfer and multiphase flow in wellbore with gas invasion was established based on the change of temperature and pressure of gas intrusion with the formation seepage, and a numerical solution method was given . Through solving the model, the calculation results show that the bottom hole pressure decreases continuously during the gas invasion process, and the rate of decrease of bottom hole pressure increases with the increase of gas invasion time. At the same time, the bottom hole temperature rises continuously, Return outlet temperature continues to decrease. According to the change law, a new method of gas invasion early detection based on combination of bottomhole pressure and wellhead temperature or bottomhole temperature and bottomhole pressure is proposed.